The present invention relates generally to internal combustion engines, and more particularly to a reciprocating counterbalance weight for balancing such an engine.
This invention relates to a counterbalance weight system for reducing the vibrational forces in an engine resulting from piston reciprocation.
A major cause of vibration in an engine is piston reciprocation. The piston is started and stopped twice during each rotation of the crankshaft, and reactions to the forces which accelerate and decelerate the piston are imposed upon the engine body as vibration in directions generally parallel to the piston axis. In installations such as lawn and garden implements, the engine produces a vibration that is transmitted through the machine to the operator. This vibration is uncomfortable and could produce operator fatigue. Even in an installation where there is no element of operator fatigue, such as sump pumps or portable generators, engine vibration is undesirable because it causes maintenance problems and tends to reduce the useful life of the machine.
To some extent such vibrations can be decreased by providing the engine with a counterweight fixed on its crankshaft, and located at the side of the crankshaft axis directly opposite the crankpin by which the piston, through the connecting rod, is connected to the crankshaft. More commonly, two counterweights may be used on the crankshaft, one located on each side of the piston axis. In either case, such a crankshaft counterweight arrangement produces a net resultant force vector that is diametrically opposite to the crankpin.
It is also known to use an additional counterbalance weight to further balance the forces due to piston reciprocation. Various arrangements are known for such counterbalance weights, including the use of pivoting and reciprocating counterbalance weights.
An engine balancing system is disclosed in which the counterbalance weight moves in a linear manner in opposition to the reciprocating piston.
In a preferred embodiment, the balancing system includes a counterbalance weight that is disposed on a second side of the crankshaft that is generally opposite to the first side on which the piston is disposed. The counterbalance weight reciprocates in response to rotation of the crankshaft. The invention further comprises an eccentric formed on the crankshaft, and at least one link arm that couples the counterbalance weight to the crankshaft. In the preferred embodiment, two spaced link arms are used.
The invention also includes at least one rail interconnected with the crankcase housing such that the counterbalance weight is slidable along the rail. One or two additional rails may be provided. Recesses or slots may be provided in the counterbalance weight that receive one or more rails. In an alternating embodiment, one or more rails may be provided, in addition to guides which keep the counterbalance weight in proper alignment, but are not themselves received within the counterbalance weight slots.
An advantage of the present invention is that the counterbalance weight moves in a linear manner in opposition to the linear motion of the reciprocating piston, for improved balancing.
Other features and advantages of the present invention would be apparent to those skilled in the art from the detailed description of the invention and the drawings, in which: